diff --git a/pkg/api/server/v1alpha2/log/s3.go b/pkg/api/server/v1alpha2/log/s3.go
index d32c661fd..fd4aa619e 100644
--- a/pkg/api/server/v1alpha2/log/s3.go
+++ b/pkg/api/server/v1alpha2/log/s3.go
@@ -161,7 +161,7 @@ func (s3s *s3Stream) ReadFrom(r io.Reader) (int64, error) {
 
 	size := s3s.partSize + n
 	if size >= s3s.multiPartSize {
-		err = s3s.uploadMultiPart(&s3s.buffer, s3s.partNumber, n)
+		err = s3s.uploadMultiPart(&s3s.buffer, s3s.partNumber, size)
 		if err != nil {
 			return 0, err
 		}
@@ -175,6 +175,10 @@ func (s3s *s3Stream) ReadFrom(r io.Reader) (int64, error) {
 }
 
 func (s3s *s3Stream) uploadMultiPart(reader io.Reader, partNumber int32, partSize int64) error {
+	if partSize == 0 {
+		return nil
+	}
+
 	part, err := s3s.client.UploadPart(s3s.ctx, &s3.UploadPartInput{
 		UploadId:      &s3s.uploadID,
 		Bucket:        &s3s.bucket,
diff --git a/pkg/api/server/v1alpha2/log/s3_test.go b/pkg/api/server/v1alpha2/log/s3_test.go
index 75a55e291..79a7d07da 100644
--- a/pkg/api/server/v1alpha2/log/s3_test.go
+++ b/pkg/api/server/v1alpha2/log/s3_test.go
@@ -50,10 +50,16 @@ func (m *mockS3Client) GetObject(ctx context.Context, params *s3.GetObjectInput,
 
 func (m *mockS3Client) UploadPart(ctx context.Context, params *s3.UploadPartInput, optFns ...func(*s3.Options)) (*s3.UploadPartOutput, error) { //nolint:revive
 	buffer := bytes.Buffer{}
-	_, err := buffer.ReadFrom(params.Body)
+	bufLen, err := buffer.ReadFrom(params.Body)
 	if err != nil {
 		m.t.Errorf("error uploading part: %d", params.PartNumber)
 	}
+	if *params.ContentLength != bufLen {
+		m.t.Errorf("ContentLength doesn't match buffer length: got %d, expected %d", *params.ContentLength, bufLen)
+	}
+	if *params.ContentLength == 0 {
+		m.t.Errorf("ContentLength must be > 0: got %d", *params.ContentLength)
+	}
 	m.body = append(m.body, buffer.Bytes()...)
 	e := strconv.Itoa(int(m.partNumber))
 	return &s3.UploadPartOutput{ETag: &e}, nil
@@ -104,19 +110,20 @@ func TestS3Stream_WriteTo(t *testing.T) {
 }
 
 func TestS3Stream_ReadFrom(t *testing.T) {
-	want := "test body of multi-part upload"
+	want := "test body of multi-part upload  40 bytes"
 	const DefaultBufferSize = 10
 	c := &server.Config{
 		S3_BUCKET_NAME: "test-bucket",
 	}
 	filePath := "test"
 	s := &s3Stream{
-		config:     c,
-		bucket:     c.S3_BUCKET_NAME,
-		key:        filePath,
-		size:       c.LOGS_BUFFER_SIZE,
-		buffer:     bytes.Buffer{},
-		partNumber: 1,
+		config:        c,
+		bucket:        c.S3_BUCKET_NAME,
+		key:           filePath,
+		size:          c.LOGS_BUFFER_SIZE,
+		multiPartSize: 20,
+		buffer:        bytes.Buffer{},
+		partNumber:    1,
 		client: &mockS3Client{
 			t:          t,
 			bucket:     c.S3_BUCKET_NAME,